It is well known that heat generating components in a computer such as central processing units, microprocessors or chipsets generate a large amount of heat during the computer operates. As the generated heat increases above a critical temperature, a failure can occur in the heat generating components. Therefore, the excess heat must be dissipated to prevent such failures.
Since a chipset is responsible for data transferring between primary chips and peripheral I/O components, it is particularly important to dissipate heat generated by the chipset. Usually, the chipset is in close contact with a heat sink for efficient heat dissipation. Such a heat sink is shown in FIG. 4 and FIG. 5.
As shown in FIG. 4, the heat sink includes a base 10 with a set of fins mounted thereon, and a plurality of fixing portions 20 disposed at lateral sides of the base 10. The base 10 is made of aluminum and the fixing portions 20 can be made of iron or aluminum alloy. As shown in FIG. 5, the heat sink is disposed on a printed circuit board 50 with the base 10 of the heat sink being in direct contact with the heat generating component 30 such as a chipset and fixing portions 20 of the heat sink being passed through the printed circuit board 50. By soldering solder balls (not shown) on the fixing portions 20 and the printed circuit board 50, soldering portions 40 are formed to fix the heat sink to the printed circuit board 50.
However, since the heat sink is made of different materials with different coefficients of thermal expansion, the heat stress is introduced which can cause such problems as cracks of the soldering portions 40 and deformations of the printed circuit board 50, thereby decreasing reliability of products.
Accordingly, there is a need to develop a heat sink which can efficiently decrease the heat stress.